ZEA MAYS 



117 



It arises at the second node, the internodal region between the 

 scutellar node and the coleoptilar node forming a short, slightly 

 elongated neck in the embryo. (Fig. 43.) The other internodes 

 are unelongated so that the embryonic leaves enclosed by the cole- 

 optile closely surround the leaf primordia and the growing point 

 of the stem axis. Two or more adventitious roots originate just 



level of scutellar 

 node on axis 



A B 



Fig. 44. A, face view diagram of scutellum showing its vascular anatomy; B, face view 

 diagram of the axis of the embryo showing the vascular system : adv rt, adventitious root; colp, 

 coleoptile; coir, coleorhiza; pri rt, primary root; pro ca, procambial strand; scu no, level of 

 scutellar node. (After Avery.) 



above the level of the scutellar node and are at first directed later- 

 ally upward. (Fig. 44, B.) The primary root has a well-defined 

 root cap; and, in the stelar portion, the differentiation of vascular 

 elements is well advanced. 



Avery (i) has described the vascular system of the embryo : 



"The embryonic vascular system consists partly of a large procambial 

 strand laid down in the scutellum. This main procambial bundle 

 branches throughout its length. In the lower part of the scutellum 

 are several procambial strands which radiate out and downward 

 from the level where they diverge from the axis. In longitudinal 

 face section they appear much like the ribs of an inverted fan. (Fig. 

 44, A.') The procambial bundles from the upper and lower ends of the 



